#include <bits/stdc++.h>
#define MAX 305000
using ll = long long;
__int128 A[MAX],B[MAX];
__int128 N,M;
__int128 teto(__int128 a,__int128 b){
ll c = a/b;
if(a%b)++c;
return c;
}
bool possivel(__int128 x){
__int128 sum=0;
for(int i=0;i!=N;++i){
__int128 necessario = teto(x,A[i]);
__int128 gastar = std::min(necessario,M);
__int128 falta = x-(gastar*A[i]);
if(falta>0){
ll precisa = teto(falta,B[i]);
sum-=precisa;
}else {
ll sobra = M-gastar;
sum+=sobra;
}
}
return sum>=0;
}
int main()
{
std::ios::sync_with_stdio(false);
std::cin.tie(0);
std::cout.tie(0);
ll a,b;
std::cin>>a>>b;N=a;M=b;
for(int i=0;i!=N;++i){long long x;std::cin>>x;A[i]=x;}
for(int i=0;i!=N;++i){long long x;std::cin>>x;B[i]=x;}
for(int i=0;i!=N;++i){
if(A[i]<B[i]){
A[i]=B[i];
}
}
__int128 l=1,r=1LL<<60LL;
while(l<r){
__int128 m=((r-l+1)/2)+l;
if(possivel(m)){
l=m;
}else r=m-1;
}
std::cout<<(ll)l<<"\n";
}
